684 research outputs found
Pensions in the laboratory: the role of commitment and reputation for deferred compensation in multi-period labor contracts
This paper examines the relationship between firms‘ wage offers and workers‘ supply of effort in a multi-period environment. If firms are able to commit to a schedule of wage payments, in equilibrium they will offer deferred compensation: first-period productivity is positive and wages are zero, while last-period productivity is zero and wages are positive. Workers respond to deferred compensation by supplying sufficient effort to avoid dismissal. In the absence of commitment, firms pay zero wages and workers supply low effort. The experiment produces strong evidence of these predictions. With commitment, we frequently observe deferred compensation and relatively high worker effort. In the absence of commitment, we observe no deferred compensation, much lower wages, and little worker effort. A third treatment where commitment is not possible, but firms are able to build a reputation, produces an intermediate result. Finally, we also find some evidence of gift exchange, in particular in the absence of commitment when deferred compensation does not work
Membrane interactions of S100A12 (Calgranulin C)
S100A12 (Calgranulin C) is a small acidic calcium-binding peripheral membrane protein with two EF-hand structural motifs. It is expressed in macrophages and lymphocytes and highly up-regulated in several human inflammatory diseases. In pigs, S100A12 is abundant in the cytosol of granulocytes, where it is believed to be involved in signal modulation of inflammatory process. In this study, we investigated the interaction of the porcine S100A12 with phospholipid bilayers and the effect that ions (Ca2+, Zn2+ or both together) have in modifying protein-lipid interactions. More specifically, we intended to address issues such as: (1) is the protein-membrane interaction modulated by the presence of ions? (2) is the protein overall structure affected by the presence of the ions and membrane models simultaneously? (3) what are the specific conformational changes taking place when ions and membranes are both present? (4) does the protein have any kind of molecular preferences for a specific lipid component? To provide insight into membrane interactions and answer those questions, synchrotron radiation circular dichroism spectroscopy, fluorescence spectroscopy, and surface plasmon resonance were used. The use of these combined techniques demonstrated that this protein was capable of interacting both with lipids and with ions in solution, and enabled examination of changes that occur at different levels of structure organization. The presence of both Ca2+ and Zn2+ ions modify the binding, conformation and thermal stability of the protein in the presence of lipids. Hence, these studies examining molecular interactions of porcine S100A12 in solution complement the previously determined crystal structure information on this family of proteins, enhancing our understanding of its dynamics of interaction with membranes
A Standard Input Format for Multiperiod Stochastic Linear Programs
Data conventions for the automatic input of multiperiod stochastic linear programs are described. The input format is based on the MPSX standard and is designed to promote the efficient conversion of originally deterministic problems by introducing stochastic variants in separate files. A flexible "header" syntax generates a useful variety of stochastic dependencies. An extension using the NETGEN format is proposed for stochastic network programs
Isolated pores dissected from human two-pore channel 2 are functional
Multi-domain voltage-gated ion channels appear to have evolved through sequential rounds of intragenic duplication from a primordial one-domain precursor. Whereas modularity within one-domain symmetrical channels is established, little is known about the roles of individual regions within more complex asymmetrical channels where the domains have undergone substantial divergence. Here we isolated and characterised both of the divergent pore regions from human TPC2, a two-domain channel that holds a key intermediate position in the evolution of voltage-gated ion channels. In HeLa cells, each pore localised to the ER and caused Ca2+ depletion, whereas an ER-targeted pore mutated at a residue that inactivates full-length TPC2 did not. Additionally, one of the pores expressed at high levels in E. coli. When purified, it formed a stable, folded tetramer. Liposomes reconstituted with the pore supported Ca2+ and Na+ uptake that was inhibited by known blockers of full-length channels. Computational modelling of the pore corroborated cationic permeability and drug interaction. Therefore, despite divergence, both pores are constitutively active in the absence of their partners and retain several properties of the wild-type pore. Such symmetrical ‘pore-only’ proteins derived from divergent channel domains may therefore provide tractable tools for probing the functional architecture of complex ion channels
Towards a population of HMXB/NS microquasars as counterparts of low-latitude unidentified EGRET sources
The discovery of the microquasar LS 5039 well within the 95% conficence
contour of the Unidentified EGRET Source (UES) 3EG J1824-1514 was a major step
towards the possible association between microquasars (MQs) and UESs. The
recent discovery of precessing relativistic radio jets in LS I +61 303, a
source associated for long time with 2CG 135+01 and with the UES 3EG
J0241+6103, has given further support to this idea. Finally, the very recently
proposed association between the microquasar candidate AX J1639.0-4642 and the
UES 3EG J1639-4702 points towards a population of High Mass X-ray Binary
(HMXB)/Neutron Star (NS) microquasars as counterparts of low-latitude
unidentified EGRET sources.Comment: 12 pages, 7 figures. Proceedings of the Conference "The
Multiwavelength Approach to Unidentified Gamma-ray Sources", to appear in the
journal Astrophysics and Space Scienc
Elastic electron deuteron scattering with consistent meson exchange and relativistic contributions of leading order
The influence of relativistic contributions to elastic electron deuteron
scattering is studied systematically at low and intermediate momentum transfers
( fm). In a -expansion, all leading order
relativistic -exchange contributions consistent with the Bonn OBEPQ models
are included. In addition, static heavy meson exchange currents including boost
terms and lowest order -currents are considered. Sizeable
effects from the various relativistic two-body contributions, mainly from
-exchange, have been found in form factors, structure functions and the
tensor polarization . Furthermore, static properties, viz. magnetic
dipole and charge quadrupole moments and the mean square charge radius are
evaluated.Comment: 15 pages Latex including 5 figures, final version accepted for
publication in Phys.Rev.C Details of changes: (i) The notation of the curves
in Figs. 1 and 2 have been clarified with respect to left and right panels.
(ii) In Figs. 3 and 4 an experimental point for T_20 has been added and a
corresponding reference [48] (iii) At the end of the text we have added a
paragraph concerning the quality of the Bonn OBEPQ potential
HAPEX-Sahel : a large-scale study of land-atmosphere interactions in the semi-arid tropics
The Hydrologic Atmospheric Pilot EXperiment
in the Sahel (HAPEX-Sahel) was carried out in Niger, West Africa, during 1991 -
1992, with an intensive observation period (IOP) in August - October 1992. It
aims at improving the parameterization of land surface atmosphere interactions
at the Global Circulation Model (GCM) gridbox scale. The experiment combines
remote sensing and ground based measurements with hydrological and
meteorological modelling to develop aggregation techniques for use in large
scale estimates of the hydrological and meteorological behaviour of large areas
in the Sahel. The experimental strategy consisted of a period of intensive
measurements during the transition period of the rainy to the dry season, backed
up by a series of long term measurements in a 1° by 1° square in Niger. Three
"supersites" were instrumented with a variety of hydrological and
(micro) meteorological equipment to provide detailed information on the surface
energy exchange at the local scale. Boundary layer measurements and aircraft
measurements were used to provide information at scales of 100 - 500 km2.
All relevant remote sensing images were obtained for this period. This programme
of measurements is now being analyzed and an extensive modelling programme is
under way to aggregate the information at all scales up to the GCM grid box
scale. The experimental strategy and some preliminary results of the IOP are
described
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